Biocompatible medical films are most often used in surgical settings as a physical barrier to help separate certain organs from adjacent tissues and medical devices following surgical intervention or blunt dissection to minimize adhesion formation. For example, SEPRAFILM®, a product of Genzyme Corporation of Cambridge, Mass., is used in patients undergoing either open or laparoscopic abdominal or pelvic surgeries as an implantable treatment intended to reduce the incidence, extent, and severity of postoperative adhesion formation between different tissues and organs and implantable medical devices such as soft tissue support membranes and mesh, or combinations of non-absorbable films and meshes.
U.S. Pat. No. 5,017,229 is directed to a water insoluble, biocompatible gel that includes the reaction product of hyaluronic acid, a polyanionic polysaccharide, and an activating agent. The gel described in the '229 patent can be provided in the form of an adhesion prevention composition, such as a membrane or composition suitable for incorporation into a syringe. The gel is described as being able to form a film by being cast into a sheet form, extruded, compressed, or allowed to dehydrate in a flat sheet. When modified with polysaccharide, the biodegradable film forms the above-described SEPRAFILM® adhesion-limiting or adhesion barrier product made commercially available as a dehydrated bio-dissolvable single layer sheet.
However, such commercially available adhesion prevention and adhesion barrier film products often can be difficult to handle and apply to the targeted location due to their chemical make up and rapid bio-dissolvable properties. The composition and limited structural strength properties of these bio-dissolvable products result in the material forming the products softening relatively quickly upon exposure to fluids, thus making handling difficult during most open and laparoscopic surgical intervention operations. Furthermore, many of these bio-dissolvable films are made intentionally to be thin and without reinforcement or anchoring support to minimize tissue disruption and consequently end up being structurally weak (i.e., easily torn or folded during handling). These characteristics of the film products result in a very low level of mechanical fixation integrity and a very low level of handling stability during surgical manipulation and implantation. These characteristics are intentional, principally to enhance rapid body fluid absorption and subsequent chemical breakdown and liquefication by body fluids for complete absorption and removal by the body. Chemically stabilized adhesion prevention film products engineered solely for adhesion prevention or temporary barrier separation are also known to be difficult to handle during surgery because of a tendency for the materials to adhere to themselves, and are known to tear and fold undesirably during handling and implantation.
Surgical meshes, which are used to reinforce weakened areas of abdominal, pelvic, or thoracic tissues, or to replace a portion of internal structural soft tissue that has neither been damaged nor removed surgically, can also be made to have anti-adhesion properties. PCT Application Publication No. WO 2004/028583 is directed to compositions, devices, and methods for maintaining or improving the integrity of body passageways following surgery or injury. Surgical mesh drug eluting delivery devices can include one or more therapeutic agents provided with a drug eluting mesh wrap implant placed adjacent to medical devices and internal tissue as described therein. The meshes are available in various single layer, multi-layer, and 3-dimensional configurations made without bio-absorbable adhesion coatings and films. The meshes are most often constructed of synthetic non-absorbable polymer materials, such as polyethylene, polytetrafluoroethylene, and polypropylene, and can include a carrier having a therapeutic agent attached thereto, incorporated within, or coated thereon. The mesh structure for this surgical application serves as a drug eluting delivery apparatus for local therapeutic delivery within the body. Affixing the carrier and or coating directly onto the surgical mesh makes it easier to handle the device without the drawbacks of film, namely tearing, folding, and rapid dissolving when contacting body fluids, and the lack of fixation or anchoring means. Non-absorbable mesh structures generally provide more handling strength and directional placement control during installation than bio-absorbable or bio-dissolvable polymer films. However, surgical mesh structures are not structurally designed to create barrier layer separation between tissue and medical devices due to their inherent porous structure. Such devices do enable some form of mechanical fixation or anchoring ability not possible with films, but the strength of the mesh structures can be insufficient to adequately hold fixation and anchoring devices without tearing, material disruption, elongation, and/or separation from its anchoring mechanism(s).
For most surgical procedures involving internal tissue reconstruction, dissection, or soft tissue repair, there is often a need to reinforce the surgically effected area with a non-absorbable implantable structure (such as a mesh or porous polymeric film). Such devices require an anchor, suture, adhesive, or tack to hold the mesh (or other device) in place within the patient's body to avoid migration, material separation, folding, wrinkling, or clumping of the implanted device after the surgery is complete.
All known implantable reinforcement devices, including non-absorbable surgical mesh and porous polymer films, are designed to promote either uninhibited cellular in-growth or limited cellular in-growth through the medical device over time. After tissue begins growing into and through the surgically implanted porous mesh or film, the implanted device is further anchored or held in place by that ingrown tissue, in addition to the surgically applied mechanical anchoring means. However, prior to such tissue in-growth, which can take days, weeks, or even months, depending on the condition of the patient and the location of the implant and damaged tissue, it is necessary to hold the mesh, or other device, in place with such fasteners as anchors, sutures, tacks, or adhesives.
These various mechanical fasteners involve either passage directly through an existing hole in the porous implant, or forcibly puncturing the implant, forming a new button hole or other aperture through the device, causing some damage to the material during the anchoring process. Apertures or points of anchoring created in the porous mesh and film devices are subject to increased mechanical stress because the fastener or adhesive applying additional force against the apertures or points of anchoring to hold the implant in place against soft tissue. These increased fixation stresses have, at times, resulted in the device becoming separated from its anchoring mechanism due to excessive material stretching and/or tearing. At the apertures or points of anchoring, the underlying tissue during normal physical activity can sometimes unpredictably pull the anchoring means through the aperture or button hole, leaving this portion of the implanted device un-anchored. Even more problematic for the medical user is, when tensioning the implant to remove folds or wrinkles, an anchored location pulls free, or pulls through the mesh device.
The tearing of the device at or near areas of anchoring mechanisms, depending on the particular fastener used, can allow the implanted device to become disrupted from its preferred location, or to lift up and off the anchoring mechanism, leaving the non-attached portion of the device disconnected from the tissue it was meant to reinforce. The excessive stretching and tearing, either during surgical installation or immediately following surgery during normal physical activity can result in complications derived from the implant becoming un-anchored or disconnected from the tissue, which can be clinically detrimental to the patient. Such detachment events are often referred to as “re-occurrences”, and generally require surgical-re-intervention, additional blunt dissection, or separation of adjoining tissues to re-establish a desirable and anatomically suitable fixation spot to re-attach the implant material. In the event the implant anchoring hole has torn or has elongated under stress conditions, often the implant cannot be repaired or re-attached at the location of the tear or stretch, thus requiring removal of the implant and/or introduction of a replacement implant device, requiring additional anchors to new tissue locations to patch over the damage caused by the events related to the first implant.
In addition to providing an inadequate means for anchoring, these implantable devices may become deformed during and/or after implantation. During implantation these reinforced implantable devices may be stretched or distorted. After the reinforced implantable device is implanted, the anatomical area it is intended to cover may have an irregular surface such that the reinforced implantable device may be distorted to conform to the irregular surface. For example, in case where a patient has an abdominal defect, the reinforced implantable device may conform to the defect, which in some cases may be an undesired result. The distorting and stretching that occurs during and/or after implantation may cause temporary or permanent deformations and reduce the effectiveness of the reinforced implantable device. These deformations may become more pronounced as the size of the reinforced implantable devices increases.